Investigation of welding of dissimilar high thickness SA106 Gr.C carbon steel and SA335P12 alloy steel to eradicate the failure in boiler components fabricated through SAW and SMAW processes

Abstract

This study reports the effect of Shielded metal arc welding (SMAW) and Submerged arc welding (SAW) processes used to fabricate high-thickness end cover plates by welding of dissimilar materials SA 335 P12 steel pipes and ASTM A 106 grade C carbon steel. The study emphasizes the structure-property relation of the welded joints made by two different techniques using macrostructure and microstructural examination with optical and electron microscopy and hardness evaluation. The joints were subjected to magnetic particle non-destructive testing and the SAW joint was found to be defect-free. Microstructural examination revealed acicular ferrite microstructure on the SAW joint but bainite and martensite microstructure on the SMAW joint. After heat treatment hardness values disclosed the dissolution of the hard phases. The joints fabricated with SAW demonstrated high ductility with an increase in elongation of 23% and 37.5%, during the bend test and the tensile test respectively. Higher thickness welding of dissimilar joints by SAW is prefereed over SMAW joints, as it requires fewer weld passes and produce superior weld quality without any defects.